1. Field of the Invention
This invention relates broadly to surgical instruments. More particularly, this invention relates to endoscopic instruments, and particularly endoscopic needles.
2. State of the Art
Endoscopic needle assemblies are used with flexible endoscopes to inject fluids under endoscopic visualization in body structures such as the esophagus, the colon, and the stomach. For example, when removing polyps from within the colon, it is customary to inject saline solution into the tissue surrounding and underlying a polyp in order to xe2x80x9craisexe2x80x9d the polyp thereby facilitating excision by means of forceps or snares. Visible dyes and radiological contrast dyes are sometimes injected to mark the location of areas explored endoscopically so that the structures can be located during subsequent procedures. Also, sclerosing agents are sometimes injected into vascular structures, such as esophageal varicoceles, in order to cause clotting and to necrose the tissue so that it can be reabsorbed by the body.
Such needle assemblies generally consist of a needle, an inner flexible tube, a flexible outer tube, a handle assembly and an injection syringe. The inner flexible tube provides a fluid pathway, and is surrounded by the loose-fitting flexible outer tube. The needle is connected to the distal end of the inner tube by use of adhesives, a stainless steel crimp band, or both, and the handle assembly is connected to the proximal end of the inner tube. Attached to the handle is an injection syringe, which supplies fluid to the fluid pathway of the inner tube when a plunger of the syringe is pushed. The inner tube is designed for the dual purpose of conducting fluids injected by a syringe located at the handle to the tissue surrounding the needle and for imparting motion produced at the handle to the needle. The handle assembly permits the user to move the inner tube in and out relative to the outer tube, thus retracting the needle into the outer tube or extending it beyond the distal tip of the outer tube. The outer tube is generally formed from a relatively flexible plastic polymer material such as PTFE or FEP. Sometimes the outer tube is also fitted with a band of stainless steel to reinforce its distal tip. The inner tube is generally formed from PTFE.
The needle assembly is designed to be inserted and fed into a smooth cylindrical working channel of an endoscope. In order to make the needle assembly flexible enough to negotiate the curves of an endoscope during use and to allow free motion of the needle assembly within the working channel of the endoscope, it is desirable to make the outer tube and the inner tube from a relatively flexible plastic polymer material such as PTFE or FEP. When the needle assembly is positioned properly within the endoscope, the needle of the needle assembly can be extended through a distal port in the endoscope by application of force on the handle of the needle assembly. When the operator applies the actuating force to the handle to extend the needle, a compressive force is applied to the inner tube, and a reactive tensile force is applied to the outer tube. Typically, the plastic inner tube is compressed and shortened and the plastic outer tube is stretched and elongated. This distortion causes the relative motion of the needle and the distal end of the outer tube to be sluggish and less than the full motion imparted to the handle on the proximal end of the device. Further, because of friction between the inner tube and outer tube, the motion of the needle relative to the distal tip of the outer tube is not immediate and direct; i.e., the force is not immediately and directly applied to the endoscopic needle assembly because the flexible polymer materials of the inner tube and the outer tube have some degree of elasticity in compression and tension and the force applied by the actuating handle is initially absorbed by the plastic material itself before it is translated into a positive and certain motion of the distal end of the endoscopic needle assembly.
Several problems result from the poor transmission of translational motion from handle to needle. First, the user must be able to move the endoscopic needle assembly relative to the endoscope""s working channel (a lumen adapted to receive endoscopic instruments therethrough) in order to position the needle relative to the end of the endoscope and to stick the needle into the desired tissue. The compressiveness of the standard plastic outer tube and its friction relative to the endoscope""s working channel and against the inner tube works against the ability of the user to precisely move the assembly in and out of the working channel. Second, it is difficult or impossible to push the needle into the tissue where an injection is desired by means of relative motion of the needle and the outer tube. Hence, the outer tube must be moved relative to the endoscope or the endoscope must be moved within the patient to effect the desired injection. Third, since the motion of the needle relative to the distal tip of the outer tube is not positive and certain, it is possible for the needle to move to an extended position when such is not desired. For example, it is possible for the needle to advance beyond the distal tip of the outer tube while the needle assembly is still within the working channel of the endoscope, which can result in internal damage to the endoscope and to the needle itself.
U.S. Pat. No. 5,601,588 to Tonomura et al. shows an endoscopic needle assembly in which the inner tube is made of metal, e.g., stainless steel or a super-elastic alloy, in order to minimize the compression in the inner tube. The needle may be formed integrally with the metallic inner tube or made as a separate part and attached to it. While the Tonomura et al. device offers an improvement to the standard all plastic construction, it also has several disadvantages. First, the stainless steel inner tube is stiffer than desired. The inner tube can be kinked if bent too tightly, and will take a permanent set if flexed beyond its elastic limit, as might be the case when the endoscope is tightly flexed while negotiating a tortuous colon or when being retroflexed. Second, a super-elastic alloy tube construction is prohibitively expensive for the intended general endoscopic use. Third, Tonomura et al. specifically does not address several problems: (1) accidental exposure of the needle within the endoscope, (2) the need for improving the tensile stiffness of the outer tube, and (3) the need for reducing the friction of the outer tube within the working channel of the endoscope to improve the user""s control of the endoscopic needle relative to the endoscope.
Other prior art exists relating to endoscopic needle devices, but none of the prior art teaches improvements in the relative motion of the inner tube and outer tube, nor in flexibility and kink resistance of the inner tube, nor in reducing friction between the outer tube and the working channel of the endoscope.
It is therefore an object of the invention to provide an endoscopic needle assembly with an improved inner tube with reduced compression and reduced likelihood of kinking resulting in better control of the needle from the endoscope handle.
It is another object of the invention to provide an endoscopic needle assembly having an outer tube with improved tensile stiffness, i.e., a relatively small amount of longitudinal stretching or compression caused by a given amount of tensile or compressive force, resulting in more direct control of the needle within the endoscope.
It is a further object of the invention to provide an improved endoscopic needle assembly with a safety shield by which accidental exposure of the needle within the endoscope is prevented.
It is an additional object of the invention to provide an endoscopic needle assembly with an improved outer tube having a friction reducing exterior surface such that friction is reduced between the outer tube and the working channel of the endoscope to improve the user""s control of the endoscopic needle relative to the endoscope.
Another object of the invention is to provide an endoscopic needle assembly with an improved inner tube having a friction reducing exterior surface such that friction is reduced between the inner tube and the outer tube to improve the user""s control of the endoscopic needle relative to the endoscope.
In accord with these objects which will be discussed in detail below, a first embodiment of an endoscopic needle assembly according to the invention generally includes an inner tube, an outer tube, a needle coupled to a distal end of the inner tube, and a handle assembly coupled to proximal ends of both the inner tube and the outer tube. The inner tube forms a fluid pathway or lumen connecting the needle with a syringe. The inner tube is formed from a low-friction material, such as high-density polyethylene, which is substantially non-elastic in tension and compression and yet is still considerably flexible. The outer tube, which is substantially non-elastic in tension and compression and yet is still considerably flexible, surrounds the inner tube such that the inner tube can move freely within the outer tube. The handle is designed such that it provides a convenient grip for the user, a connection for an injection syringe, and serves as a means for moving the inner tube axially relative to the outer tube.
According to a first preferred aspect of the first embodiment of the invention, the inner tube is formed having a tube-on-coil construction formed from a close-wound coil of stainless steel wire covered by a close fitting tube of a low-friction material, such as high-density polyethylene.
According to a second preferred aspect of the first embodiment of the invention, the outer tube is also formed having a tube-on-coil construction formed from a close-wound coil of wire covered by a close fitting tube of low-friction material.
According to a third preferred aspect of the first embodiment of the invention, a safety shield formed from a plurality of hinged petals is provided at the distal end of the outer tube to protect the endoscope from inadvertent penetration by the needle in the endoscope. The petals are held shut by an elastic element, but can be opened by application of a small force applied at the handle of the endoscopic needle assembly which moves the inner tube and needle relative to the outer tube and through the petals. When the endoscopic needle assembly is within the working channel of the endoscope, the petals cannot be expanded and the outer tube moves freely in and out of the working channel of the endoscope. When the petals are expanded, it is not possible to retract the outer tube back into the working channel of the endoscope; and thus the needle is prevented from contacting or penetrating the endoscope.
According to a fourth preferred aspect of the first embodiment of the invention, in order to reduce friction between the inner tube and the outer tube and/or between the outer tube and the working channel of the endoscope, the inner tube and the outer tube or combinations thereof are designed to have relatively different cross-sectional shapes.
Alternatively, the inner tube of the first preferred embodiment may be formed from a similar flexible low-friction material, such as high-density polyethylene, having a piece of a thin metal wire attached at a specific segment along the interior of the flexible inner tube. The piece of wire,provides the segment of the inner tube with a measure of rigidity in tension and compression. The short length of wire may also be used to strengthen a segment of the inner tube which has a reduced diameter. Further, the alternate embodiment may also incorporate a first preferred aspect, a tube-on-coil construction outer tube; a second preferred aspect, a safety shield attached to the outer tube; and a third preferred aspect, an inner tube and an outer tube having relatively different cross-sectional shapes.
A second embodiment of the invention generally comprises a thin metal actuating wire, an outer tube connected to a syringe, a needle coupled to a distal end of the thin wire, and a handle coupled to proximal ends of the thin wire and outer tube. The thin metal actuating wire, which runs the full length within the flexible outer tube, is coupled to the needle and is used instead of an inner tube to communicate the motion imparted by the handle to the needle at the distal end of the endoscopic needle assembly. Proximal and distal sliding seals surround the thin wire and the needle, respectively, and effectively cause the outer tube to become an enclosed fluid channel, with the needle remaining in fluid communication with the syringe.
According to a first preferred aspect of the second embodiment of the invention, the outer tube is formed having a tube-on-coil construction formed from a close-wound coil of stainless steel wire covered by a close fitting tube of a low-friction material, such as high-density polyethylene. The outer tube provides a fluid pathway between the needle and a lumen of the syringe.
According to a second preferred aspect of the second embodiment of the invention, a safety shield is built onto the distal end of the outer tube to protect the endoscope from inadvertent penetration by the needle in the endoscope while the endoscopic needle assembly is within the working channel of the endoscope.
According to a third preferred aspect of the second embodiment of the invention, the outer tube may be formed having a non-circular cross-section which reduces the friction between the outer tube and the working channel of the endoscope.
A third embodiment of the invention generally comprises an inner tube, an outer tube, a thin metal actuating wire, a handle and a needle. The thin metal actuating wire runs the full length of the flexible inner tube. It is coupled distally to the needle and proximally to the handle, and is used to communicate the motion imparted at the handle to the needle at the distal end of the endoscopic needle assembly. A syringe, attached to the endoscopic needle assembly, is in fluid communication with the inner tube and the needle. The syringe delivers fluid to the needle through a fluid pathway formed by the inner tube. Further, the third embodiment may also incorporate a first preferred aspect, a tube-on-coil construction outer tube, a second preferred aspect, a safety shield attached to the outer tube surrounding the needle, and a third preferred aspect, an inner tube and an outer tube having a non-circular cross-section.
With the above embodiments and preferred aspects the following advantages are attained: improved tensile and compressive strength of the inner and outer tube which improves control of the endoscopic needle assembly; reduced friction between the inner and outer tube, and between the outer tube and the working channel of the endoscope, both of which also improve control and maneuverability of the endoscopic needle; and reduced likelihood of inadvertent penetration of the needle into the endoscope.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.